Rifles, such as the AR-15 and its derivatives include a forward assist. The forward assist is usually located near the bolt closure. When the forward assist is actuated, it pushes the bolt carrier forward, ensuring that the bolt is locked. It is commonly incorporated into standard loading procedure to prepare a weapon for firing, or to close the bolt when the weapon is excessively dirty. It can also be used to close a bolt that was gently let down, rather than released under full spring compression, to keep the noise of closing the bolt to a minimum.
In addition, many semi-automatic firearms, including the AR-15 include a bolt catch. A bolt catch is a lever usually under the bolt that engages the bolt after the last round is fired. When the last round is fired, the bolt comes back to complete the cycle and eject the round. As the bolt reaches the rearward position, it is caught by a pin or lever of the bolt catch. The bolt catch holds the bolt in a rearward position, thereby allowing the magazine to be replaced and the following round to be chambered without charging the action. The bolt catch includes a release mechanism that allows a user to move the bolt catch from an engaged to a disengaged position.
The forward assist and the bolt catch release are typically placed so as to facilitating the preferences of a right-handed shooter. In addition, the bolt catch release is typically placed in a position such that one or both hands must be removed from the firing position in order to actuate the release.